1. Field of the Invention
The present invention relates to a navigating apparatus and method which are capable of displaying a bird's eye view of a road map and which are applicable to a vehicular route guidance system or to a portable navigating apparatus.
2. Description of the Background Art
Conventionally, various types of navigation systems and methods which have been applied to route guidance systems of vehicles or to portable navigating apparatuses and methods have been proposed.
Display modes in almost all navigating apparatuses are generally top views as found in road maps of atlas. In addition, in a case where a navigating system operator (user) wants to view an information on a certain traffic intersection, an enlarged view indicating this intersection is displayed (superimposed) around a center of a displayed image screen with this intersection as a reference point. However, it is difficult for the user to grasp where a recommended route to a destination except a displayed recommended route is present, kinds of roads (road attributes, for example, freeway or national highway) and whether left and right turns (corners) are present or not due to a restriction imposed on the screen of an image display block (unit).
To solve the above-described problem, a previously proposed navigating apparatus has been proposed. FIG. 1 illustrates a functional block diagram of the previously proposed navigating apparatus. The previously proposed navigating apparatus shown in FIG. 1 includes: a calculation processing block 101 having a data access block 102 which is so constructed as to execute accesses of data to various data input from its external blocks, a reduced scale transformation block 103 which is so constructed as to transform a reduced scale of data, and an image data output block 104 which is so constructed as to output data from the reduced scale transformation block 103; a road map data storage block 105 which is so constructed as to store a plurality of road map data; a vehicle present position detecting block 106 which is so constructed as to to detect the position of the vehicle; a display reduced scale factor input block 107 which is so constructed as to input a command to switch a scale factor of the road map data to be displayed; and an image display block 105 which is so constructed as to display the reduced scale road map on a television monitor screen of display.
In operation, in a case where an area surrounding a present position of, for example, a vehicle is desired to be displayed by the user, through the display reduced scale factor input block 107, a display mode of the image display block 108 is switched into a relatively narrow region of a road map surrounding an intersection near to the present position.
Next, in a case where an information of a relatively wide region of the road map such as a direction of the destination to which the user has desired to reach and the recommended route of travel is desired to be displayed, through the display reduced scale factor input block 103, the display mode of the image display block 108 is switched into the relatively wide region of the road map. In these cases, the road map reduced scale transformation block 101 in the calculation processing block 101 serves to execute the desired and the reduced scale displays. In other words, the execution of the desired display is carried out by selecting the scale factor of the road map in the reduced scale mode.
However, in the previously proposed navigating apparatus shown in FIG. 1, when a part of the recommended route to the destination which is remote from the present position is desired to be grasped from the displayed road map, it is necessary to switch the display mode of the image display block 108 into the mode of relatively wide region of the road map. In this case, a shape of any one of the intersections on the route which would be approached to an immediate front part of the user is extremely constricted so that the user cannot easily grasp the above-described part of the recommended route which is remote from the present position. In addition, since a tiresome or complicated operation is needed via an operation switch installed on the reduced scale factor input block 107, an operability of the previously proposed navigating apparatus is reduced.